Hi Ron,

I'm told 3dm works fine going from Rhino to MoI and back. There might be some issues with layers, but perhaps Michael can be more specific.
It's SUPERB going into KeyShot. I would recommend exporting as OBJs (not 3DM) for KeyShot as MoI3D has one of the finest meshers around-- in fact some NURBS people buy it just for the mesher.

Exporting as OBJ vs 3DM also allows for faster rendering and supports some features in KeyShot which spline rendering does not.

HTH